Sgarbossa criteria LBBB:
Left Bundle Branch Block or Ventricular paced rhythm, itself makes an ECG complex enough to differentiate from a true ST elevation Myocardial Infarction (STEMI).
New ECG changes indicative of LBBB should be considered and treated as pathological unless otherwise proved. However, the job is not quite easy. Sgarbossa criteria defines a diagnostic scoring system based on ECG changes associated with LBBB and STEMI. A score of 3 or more is specific for STEMI in LBBB. The Sgarbossa criteria is as under:
- ST elevation ≥0.1 mV in one or more leads in the same direction as the QRS, in the leads where the QRS complex is positive (concordance) – 5 points
- ST depression ≥0.1 mV in one or more leads in the same direction as the QRS in V1 to V3, where the QRS complex is negative (concordance)- 3 points
- ST elevation ≥0.5 mV in one or more leads in the opposite direction as the QRS (Excessive discordance) – 2 points
Disadvantages of Sgarbossa Crieteria:
Sgarbossa criteria is very specific (98%) for STEMI in LBBB, but not sensitive (only 20%). That’s a big problem for a screening ECG.
Modified Sgarbossa criteria:
Smith, Stephen W modified the Sgarbossa criteria to make it more accurate and sensitive (upto 90%). The modification is for Sgarbossa criteria no 3 mentioned above. The modified Sgarbossa criteria is:-
ST elevation or depression ≥0.5 mV in one or more leads in the opposite direction as the QRS (Excessive discordance) with a ST/S ratio of 0.25 or less
ST/S ratio of 0.25 or less means the ST deviation is bigger than 25% of the S wave amplitude.